CO2 is released from fires (red dots) like these near Lake Malawi in southern Africa in October 2009 for agricultural land clearing. Credit: NASA

Deforestation. The environmental implications of the word are as numerous as the syllables. And scientists like Jim Collatz have the job of trying to ferret out and prove those implications. Or, as the case may be, of correcting what scientists have believed to be true.

When farmers or loggers chop or burn forest land, they set in motion the loss of biodiversity and habitat, as well as soil erosion. Collatz and other scientists are just as concerned — maybe even more so – with the carbon dioxide (CO2) deforested areas contribute to the atmosphere, warming the climate.

In 2005, the U.N. Food and Agriculture Organization announced that forest loss accounts for more than 20 percent of global emissions of CO2 from human activity. If we could stop cutting down trees, some argued, we could make a serious dent in the global carbon problem.

Not so much, a new study in the November 2009 issue of Nature Geoscience suggests. A group of Dutch and American climate scientists, including Collatz, assert that the UN’s estimate of atmospheric CO2 caused by deforestation is substantially overstated – by as much as 40 percent. Recalculating the 2005 figure with updated satellite-based estimates on carbon emissions, the researchers calculated the relative contribution of deforestation and forest degradation to be only about 12 percent.

What On Earth: How do you account for the change in the share of atmospheric CO2 from forest loss?

Collatz: New emission estimates from tropical deforestation are somewhat lower than in the past. At the same time, fossil fuel emissions are increasing rapidly. Deforestation is becoming a smaller proportion of total human-caused CO2 emissions. So, even if we could stop it completely, it would not be a substitute for decreasing fossil fuel emissions. If deforestation were 20 percent, then decreasing it to 10 percent may be significant and plausible. But since new analysis shows deforestation is closer to 10 percent, it’s unlikely that it can be reduced to zero percent.

What On Earth: What are the implications of your findings?

Collatz: Somemight read the paper and argue for less attention toward reducing deforestation.Butweneed to remain vigilant in this area. Forests provide other valuable services besides storing carbon: biodiversity, food, fiber, water resources, soil resources.Even though current rates of deforestation may be lower than previously thought, vast amounts of carbon are stored in forests and soils all over the globe and are vulnerable to climate change and land management practices.We need to monitor these carbon stocks and manage them for preservation and sequestration, or we may see unexpected increases in atmospheric greenhouse gases that go beyond what is emitted from fossil fuel burning.

In one hallway of this meeting, someone will tell you about the atomic properties of rocks; around the corner, someone will explain the motion of entire continents. You can walk into a room and learn how the solar system began, then into another to hear about how it might end. It reminds me of Robert Frost: “Some say the world will end in fire, some say in ice…”

For those of us who love earth science, the AGU meeting is a smorgasbord, and I have been bellying up to the buffet since 1995. The menu this year includes more than 15,516 choices — scientific posters, lectures, and presentations — spread over five days.

The AGU is one of the weeks when I most love my job. I get to learn what will be in tomorrow’s textbooks, museums, and classrooms, and observe science history as it is being written. Which findings will hold up and which will be rejected? It’s a privilege to be around for the debate.

Perhaps Dorothy, from the famed film Wizard of Oz, should have hoped for a fall or wintertime drought. According to findings from a NASA-funded study published last June in Environmental Research Letters , dry fall and winter seasons in the southeastern United States mean it is less likely that Southern twisters will develop in springtime to sweep anyone off their feet.

Using rainfall data from NASA satellites, rain gauge information, and NOAA’s Storm Prediction Center tornado record dating back to 1952, University of Georgia meteorologists Marshall Shepherd and Tom Mote and Purdue University climatologist Dev Niyogi discovered a statistical tendency for drought-ravaged fall and winter seasons to pave the way for “below normal tornado days” in spring seasons that follow.

“This is conceptually similar to what Bill Gray’s been doing for more than 25 years when he predicts how active the hurricane season will be based on African rain,” said Shepherd, the study’s lead author, of the Colorado State University’s pioneer hurricane season forecaster.

They culled data from Northern Georgia and other parts of the southeast, but Shepherd and his colleagues believe their findings may have relevance for other regions. The new study also adds to the body of related work Shepherd and Niyogi are ushering, including their study earlier this year in the aftermath of Atlanta’s spring 2008 twister that linked urbanization and drought to tornado activity.

For Shepherd in particular, there’s no place like home when considering the geographical focus of much of his meteorological research. “Science is my proverbial yellow brick road,” explained Shepherd. “It’s taken me down some fascinating paths, especially in learning more in recent years about tornado phenomena in my own backyard.”

NASA scientist Paul Newman briefly stopped in Cairo, Egypt, on his way to the Montreal Protocol meeting in Port Ghalib. Credit: Paul Newman

The view of the Red Sea was spectacular, but it was all work and no play for NASA atmospheric scientist Paul Newman during a recent trip to Port Ghalib, Egypt. That’s where scientists, policymakers, and representatives of the United Nations Environment Programme, convened Nov. 4-8 for an annual meeting to discuss and amend the Montreal Protocol — the international agreement that regulates ozone-depleting substances. Newman attended as co-chair of the Scientific Assessment Panel and gave us an inside look.

Q: Scientists use satellites and computer models to better understand the recovery of the ozone layer. How does this kind of science contribute to the policy decisions?A: The Montreal Protocol regulates gases that destroy ozone, also known as ozone depleting substances (ODSs). The most famous of these are the chlorofluorocarbons (CFCs) that were used in spray cans and as refrigerants. Science provides that foundation for the Protocol. We used (and still use) models to predict the evolution of ozone in our atmosphere in response to the regulations made by the signatory countries. Satellite, aircraft, balloon, and ground observations provide a check on our model estimates. If you can’t simulate the past, it’s hard to claim that you can predict the future.

Q: What is involved in a typical day as “co-chair of the scientific assessment panel”? A: We’re commonly referred to as the SAP. Not a great acronym for the scientists! In any case, we are the “on-the-spot” science advisors on all policy questions.

In a typical day, there is a lot of discussion amongst the delegates about technical issues. Delegates actively discuss “critical use exemptions.” For example, methyl bromide is used as a fumigant. Plants, flowers, vegetables are all fumigated to help preserve them or to stop the spread of invasive species such as fruit flies. Without some sort of fumigation, entire farming industries might be destroyed. However, methyl bromide is also an ozone depleting substance. The SAP provides information on methyl bromide as an ozone depleting substance. For example, if we stop all methyl bromide usage, how much will this help the ozone layer?

Q: Why is there the need to revisit the Montreal Protocol with regular meetings?A: The Protocol was designed to be an evolving agreement. Originally, the production of ODSs was limited, not stopped. Over the years, policymakers strengthened the original agreement such that all CFC production is now stopped. However, there is still some usage in developing countries, and there are stocks of ODSs that could potentially be destroyed. The nations get together twice per year to talk over the needs for evolving or strengthening the agreement.

Q: What are hydrofluorocarbons (HFC’s), and why do you think a proposal to include HFCs in the protocol was unsuccessful this year?A: Hydrofluorocarbons, or HFCs, are used as refrigerants, and they don’t destroy ozone. However, HFCs are powerful greenhouse gases.

When CFCs were banned, alternative refrigerants were developed to take their place. The initial alternatives were hydrochlorofluorocarbons (HCFCs). HCFCs were still ozone depleting substances, but they had much shorter lifetimes than CFCs, and hence, were less ozone dangerous than CFCs. In 2007, the HCFCs were banned under the Montreal Protocol and are now being phased out.

HCFCs are now being replaced by HFCs. The Montreal Protocol shifted from the ozone dangerous CFCs to the less dangerous HCFCs, and now to the ozone safe HFCs. By banning CFCs, the Montreal Protocol had a double benefit: less ozone depletion and less greenhouse gas warming (CFCs are powerful greenhouse gases).

However, by banning CFCs, the Montreal Protocol created a demand for the ozone-safe HFCs (people still want air conditioners). All of the climate benefit gained by banning CFCs might be lost as HFCs increase in our atmosphere. Hence, some people are calling for the banning of HFCs under the Montreal Protocol, in spite of the fact that HFCs don’t destroy ozone. By banning HFCs, the Montreal Protocol would become both an ozone treaty and a climate treaty.

The HFC amendment did not go through for a number of reasons. The primary reason is that many countries believe that HFCs are climate related and should therefore be regulated under the Kyoto Agreement.

Q: What current research do you think could impact future meetings?A: The Montreal Protocol is evolving into both an ozone and climate agreement. It is still necessary for scientists to investigate the impact of human-produced chemicals on both ozone and climate. Every day new chemicals are being proposed for various uses, and the scientists need to assess the environmental impact to select those chemicals that are non-toxic and environmentally safe.

The image shows estimates of rainfall for the southeastern United States from September 14–21. The estimates, acquired by multiple satellites, are calibrated with rainfall measurements from NASA’s Tropical Rainfall Measuring Mission (TRMM)satellite. The highest rainfall amounts—more than 300 millimeters (11.8 inches)—appear in blue. The lightest amounts appear in pale green. Credit: NASA/Jesse Allen

For the past four years, drought has parched the soil of north Georgia farms, nearly drained Atlanta’s 38,000-acre reservoir, and left area lawns brown. Then in just eight days in September 2009, the region’s weather took a turn that likely had residents asking if they were on a climate seesaw.

As millions of Georgians watched and as many fled for higher ground, meteorological forces coalesced to deliver heavy rains and flooding not seen in the southeastern U.S. in more than 100 years, according to the National Weather Service.

Millions of dollars of property were destroyed, and ten lives were lost. The flooding dominated local TV news and compelled the governor to declare a state of emergency across 17 counties.

Even before the rains ended, research meteorologist, Marshall Shepherd a professor of Atmospheric Sciences at the University of Georgia, and colleagues began piecing together rainfall and soil moisture data from NASA satellites, Doppler radar, weather reports and ground-level rain gauges to assemble a clearer picture of the climatological factors that fueled the flooding.

Though not yet peer reviewed, Shepherd’s initial findings suggest what may have prompted the downpours and floods. Moisture from the Gulf of Mexico was drawn into the southeast by a stalled low pressure system from the Mississippi Valley. The moist air and a series of meteorological disturbances merged with a key ingredient – a dramatic increase in urban land cover – to bring this historic weather event to the region for the second time in as many years.

“We had days and days of downpours and an extraordinary 24-hour rainfall event at the end of that period. With soil moisture already at a high, the rain could no longer infiltrate the soil and we reached a tipping point for flooding,” explained Shepherd, a native of metropolitan Atlanta who NASA has funded to investigate how urban land cover and pollutants affect rainfall and surface water changes.

“The rain and the soil moisture content combined to overwhelm rivers and streams,” he said. “Add to that Atlanta’s impenetrable roads and sidewalks, which increase the volume of runoff, and you get the event of record we witnessed.”

According to Shepherd, the long drought in the southeast – which caused job losses in agriculture and lawncare and other water use hardships across many sectors of society — is now over.

“In fact, October is normally the driest month in North Georgia,” Shepherd said. “But this year, sea surface temperature data from NASA and NOAA satellites tell us a moderate El Nino in the Pacific appears likely to lead to a cooler and wetter fall and winter in the Southeast.”

Curiously, drought may be the last of Atlanta residents’ weather worries in the next season or two to come.

Many of you may be thinking: “NASA does Earth science?I thought you blast robots to Mars, send astronauts to the space station, and build all of those great orbiting telescopes.”Sure, we do all that.

But in fact, NASA is also the leading funder of Earth research in the United States. The agency has more earth scientists on staff than any other institution in the world. We’d like to tell you more about their work.

The “What On Earth” blog is composed by the science writers, producers, and educators who cover NASA from the inside. We are former journalists and scientists; communications majors and science majors; news hounds and would-be poets. We work with NASA-funded scientists to tell their stories; periodically they will write for themselves in this forum.

Our goal is to provide glimpses of the everydays of Earth science — the field campaigns, lab experiments, technology development – that illuminate the work behind the breakthroughs. We hope to share the evolution of scientific thinking and debates, and the practical application of NASA science in society.Most of all, we want to share the fun we have watching science in progress.